Magnetic separation of positive and negative ignitor firing pulses



4, 1956 B. D. BEDFORD MAGNETIC SEPARATION OF POSITIVE AND NEGATIVEIGNITOR FIRING PULSES Flled Aprll 25, 1955 L l I J T Tl L J Inventor:Burn/0e05edford, gZ 4%ZZ/%7M H/SAttorheg United States Patent 2,759,126MAGNETIC SEPARATION or rosrr-lvn A1 NEGATIVE IGNITOR FIRING PULSE'SBnmipe D. Redford, Scotia, N. Y., assignor to General Electric Company,a corporation of New York Application April '25, 1955, Serial No.503,695

11 Claims. ('Cl. 315- 252) This invention relates to ignitor firingcircuits for vapor electric discharge devices employing a pool-typecathode and an ignitor immersed therein for initiating the discharge ofsaid device. I

in order to obtain the desired recision of operation of the electricdischarge devices of the type contemplated herein, a supply circuit isusually provided which impresses voltages of predetermined Wave form,such as voltages of peaked wave form, on the ignitors or startingelectrodes thereof. Only a small inverse voltage is pen missible on theignitors or starting electrodes of such discharge devices or they willeither be destroyed or the life thereof will be materially reduced. As aconse quence, it is common practice to couple the ignitors of thedischarge devices to the supply circuit by means of a transformer,connecting each ignitor in series a unidirectional current conductingdevice and connectin the series combination across the transformeroutput sir cuit. The unidirectional current conducting devices are poledto pass current in a direction to initiate discharge of the device andblock or eliminate reverse current half cycles of the alternatingcurrent supply. The unidirec' tional current conducting devices aregenerally rectifiers' of the selenium type which are subject to failureparticularly if the rating of the rectifier is not high enough. Failureof the rectifiers result in either immediate destruction of theassociated ignitor or a substantially reduced life thereof.

Since the rectifiers employed are subject to failure and since they arerelatively expensive, particularly in the high rating groups, it isdesirable to provide firing circuits wherein such rectifiers are notrequired. One such cir= cult is disclosed in the co-pending applicationof Harry L. Kellogg, Serial No. 266,526, filed January 15, 1952, nowPatent No. 2,730,661, and entitled Initiating the Arc in Mercury PoolTubes and which is assigned to the assignee of my present application.In most circuits devised to eliminate such blocking rectifiers, however,the output transformers used to supply the ignitor potential must beconstructed of square loop magnetic material and narrow peak firingcircuits must be used if the circuit is to be effective. Obviously, ifthe rectifier eliminating circuit is not efiective the life of theignitors of the electric discharge devices will have a short life.- Itis, of course,- an added expense to construct the output transformers ofa square loop magnetic material and it is also an added expense toprovide firing circuits of the narrow peak type. This being the case,-it may notbe economically feasible to eliminate the rectifiers by theuse of such equipment.

Accordingly, it is an object of this inventionto provide an improvedenergizing circuit for starting electrodes of pool cathode type valveswherein the application of reverse voltages on the starting electrodesis substantially eliminated, which utilizes ordinary magnetic materialin the magnetic core inductive devices employed, and wherein the firingpotential applied is of a wave form having ordinary peak widths.

2,759,126 Patented Aug. 14, 1956 Another object of this invention is toprovide an improved energizing circuit for startingelectrodes of poolcathode type valves wherein the application of reverse voltages on thestarting electrodes is substantially eliminated without the use ofblocking rectifi'ers, wherein ordinary magnetic material is used for themagnetic cores of inductive devices employed, and wherein the wave formof the ignitor firing potential has peaks of ordinary widths.

Briefly stated, in accordance with the inven'ti'on, the usual blockingunidirectional current conducting devices may be eliminated or theratings of the rectifiers required are substantially reduced byproviding saturable core impedance devices in the primary circuits ofthe igritor potential supplying circuit which devices are saturated insuch a manner as to pass positive firing peaks or half cycles andsubstantially reduce the magnitude of negative firing peaks or halfcycles. In this way, the positive and negative ignitor firing pulses orpeaks are separated by magnetic means.

The invention both as to its organization and method of operation willbe better understood from the following description taken in connectionwith the accompanying' drawing in which: 7 Y

Fig. l is a schematic representation of a pair or metc'ur'y pool cathodedischarge devices in their associated ignitor fiiilig circuits, in whichthe invention brie of its forms is embodied; and p I V Fig. 2 is aschematic representation similar to the representations of Fig. 1illustrating the invention in another of its terms. 7

In the circuits schematically represented in Figs. 1 and 2 of thedrawing a pair of vapor electric discharge devices 10 and 11 employingpool type cathodes 12 and ignitor's '13 immersed therein for initiatingthe discharge of said device is used. The dis charge d evices 10 and 11are also provided with anodes Illa and 11d; respectively. The cathodeand anode circuit'sof these valves are not shown since the specificarrangement of their eiem ponents forms no part of this i'nvention butterminals C and A, respectively, are brought out to i'ndic'at'c theposinon of Such connections. It will be understood, however, that thevalves may be arranged to act as rectifier's iii a Well-known manner orthey may be arranged to act as inverters, which is also a well-knownconnection. I In any case, the invention is applicable to the typevalves contemplated herein when operated as either rectifir's tar asinverters. Also,- the invention is applicable to are use of single valvesuch as valve 10 or ya'lve 11 Referring particularly to Fig. 1, it Willbe seen that the energizing circuit for the ignitors 1 3 is suppliedfrom an alternating current source 14. As illustrated a wave peakingcircuit 15 is connected in series with al current limiting and blockinglinear reactor 16 across the altern'atifig current source 14 and asecond wave peaking circuit 15a is connected cascade with the first. Thewave peaking circuits l5 and 15a are employed is provide alternatingcurrent voltage of peaked wave form to Be applied to the ignitors 13 ofthe valves 10 and 11. As illustrated, each peaking circuit is of thetype disclosed and claimed in U. S. Patent 2,431,933, granted Deccabet2; 1947, en application of E. F. Arexanderscn and A.-

Mittag. 7

The Wave peaking circuit 15 comprises a satiirable firing reactor 17,and a firing capacitance I8, which regether constitute a resonantcircuit of the non-linear one; That is, the circuit is non-linearlyresonant with respect to the magnitude of the voltage of source 14, theinducti-ve react-ance of firing reactor 17 having a value which issubstantially greater than the capacitive reactance of its supplycircuit within the lower region of the soiirce voltage, and smaller thanthe capacitive reactance thereof within the upper region so that animpulse of voltage is produced when the firing reactor 17 saturates.These impulses occur twice during each cycle of voltage at timesrelative to the supply voltage wave which are determined by thesaturation of a non-linear firing reactor 17. The linear reactor 16 isconnected between the voltage source 14 and the peaking circuit 15 toprevent discharge of the capacitor 18 back to the voltage source and tolimit the magnitude of the current derived from the supply.

The peaking circuit 15a has a firing reactor 17a and a capacitor 18a,which correspond in function to the like component 17 and 18 on thepeaking circuit 15. The use of the two peaking circuits in cascadeprovides a better peaking. By better peaking, it is meant a circuitwhich supplies a wave form having narrower peaks. The output of thepeaking circuit 15a is connected directly across the series combinationof a primary winding 19 of an output transformer 20 and the main winding21 of a saturable core impedance device 22. In addition, the peakingcircuit 15a is connected across the series combination of the primarywinding 23 of output transformer 24 and the main winding 25 of saturablecore impedance device 26. That is, the two series circuits referred toare connected in parallel with each other and across the output of thepeaking circuit 15a. The secondary or output winding 27 of the outputtransformer 20 is connected directly across the ignitor and cathode 13and 12, respectively, of the valve and the output transformer 24 has itssecondary or output winding 28 connected to supply the ignitor potentialto the ignitor 13 of the discharge device 11.

The saturable core impedance devices 22 and 26 have biasing windings 29and 30, respectively. As indicated in Fig. 1, these biasing windings (29and 30) are connected in series and are energized from a source ofdirect current indicated by the numeral 31. The direct current source 31is preferably of suflicient magnitude to provide enough ampere turns tosaturate each of the saturable impedance devices 22 and 26. The biasingwindings are connected in the direct current circuit in such a mannerthat their magnetizing action on their respective reactors is to aid themagnetizing eflFect of a positive firing half cycle flowing in the mainwinding and oppose the magnetizing efifect of a negative ignitorcurrent.

Reactors 22 and 26, offer very little impedance to a positive firingcurrent in their respective circuits since they are already saturated inan aiding direction but present a very high impedance to negativeignitor cur rents which tend to build up ampere turns in opposition tothe established direct current ampere turns. Thus, currents which are ofa sense to supply positive firing peaks in the circuits of the ignitors13 of the two valves 10 and 11, respectively, will pass substantiallyunimpeded through circuits of the primary windings 19 and 23 of theignitor potential supplying output transformers 20 and 24, respectively,while currents caused by negative firing potentials in the circuits ofthe valves will be suppressed or substantially eliminated by'thesaturable core impedance devices 22 and 26.

With the circuit just described, the magnetic separation of positive andnegative firing pulses can be accomplished with relatively smallreactors in series with the primary windings of each output transformer.If the: series saturable core reactors 22 and 26 are made larger and thebias thereon made correspondingly larger, then these devices may be usedto control the time of ignitor firing in the valve associated with therespective circuits as well as separating the positive and negativefiring: peaks. Also, one of the peaking circuits may be eliminated ifthe bias reactors 22 and 26 are made sufficiently large.

The circuits shown diagrammatically in Fig. 2 of the drawing are evenmore effective in separation of the posi- 4 tive and negative peaks withordinary magnetic material in the output transformers and saturable coreimpedance devices than the circuit of Fig. l. The elements of Fig. 2which correspond to those of Fig. 1 are given like reference numeralsfor brevity of description.

The circuit of Fig. 2 also utilizes the source of alternating current14, a linear blocking and current limiting inductor 16 in seriestherewith, a pair of cascade connected firing circuits 15 and 15a, and apair of saturable core reactors 22 and 26 which have main windings 21and 25, and biasing windings 29 and 30, respectively. It will also beseen that the biasing windings 29 and 30 are connected in the samemanner as the biasing windings 29 and 30 shown in Fig. 1 across a directcurrent source 31.

In the embodiment of the invention illustrated in Fig. 2, saturabletransformers 32 and 33 are provided to supply the ignitor potentials forthe valves 1% and 11, respectively. The ignitor potential supplyingtransformers 32 and 33 are provided with primary or input windings 34and 35, respectively, output or secondary windings 36 and 37,respectively, and separate biasing windings 38 and 39, respectively.Each primary winding is connected in series with the main winding of oneof the individual saturable core impedance devices 22 and 26. That is,the primary winding 34 of the ignitor potential supplying transformer 32is connected in series with the main winding 21 of the saturable coreimpedance device 22 and the primary winding 35 of the transformer 33 isconnected in series with the main winding 25 of the saturable coreimpedance device 26. Each of these series circuits is connected acrossthe output of the peaking circuit 151; and in parallel with each other.

Since the biasing windings 23 and 39 of the two saturable core impedancedevices 22 and 26 are connected as described with reference to thecircuit of Fig. 1, each of the saturable core impedance devices presentsa very high impedance to a negative firing pulse in its series circuitand practically no impedance to a positive firing pulse therein. That isto say, the saturable core impedance devices 22 and 26, act to separatethe positive and negative ignitor firing pulses as previously described.The biasing windings 38 and 39 on the output transformers 32 and 33 areprovided to supplement this peak separating action.

As illustrated the saturable transformer biasing windings 38 and 39 areconnected in series with each other across a direct current source 40.The biasing windings are wound on their cores in such a manner thattheir magnetizing action on their respective transformer cores is to aidthe saturation of the core when a negative firing pulse is applied tothe primary winding of the particular transformer. That is, the biasingwindings 38 and 39 are wound on their respective transformer cores sothat the magnetic effect of the current flowing in the biasing windingis to aid the magnetic effect of the current of a negative firing pulsein the primary winding and to oppose the magnetic effect of a positivehalf cycle of current flowing therein. In this way, the flux in eachtransformer will be changed substantially due to a positive half cycleof current from the circuit 15a while the flux would not changeappreciably due to a negative half cycle of current from the peakingcircuit 15a. Under these circumstances, positive firing potentials willbe very effectively induced across the potential supplying transformersecondary windings while onl ya minimum negative firing potential canbe.

It will be appreciated that a positive firing half cycle in the supplycircuit of the valve 10, that is, in the circuit of the transformer 32,represents a negative firing half cycle in the supply circuit of thevalve 11 and vice versa (in the circuit of the primary winding 34 of thetransformer 33). With this arrangement, both the saturable coreimpedance device 22 and the saturable transformer 32 tend to eliminatenegative firing potential on the ignitor 13 of the valve and both-thesaturable core impedance device 26 and the saturable transformer 23cooperate substantially to eliminate the occurrence of a negative firingpotential on the ignitor 13 of the valve '11. Due to the condition oftheir cores, however, none of the saturable impedance devices referredto tend to suppress or eliminate the positive firing potentials on theignitors. Thus, with this arrangement a very effective magneticseparation of the positive and negative firing peaks is obtained.

Although I have described above particular embodiments of my invention,any modifications can be made, and it is to be understood that I intendto cover by the appended claims all such modifications as fall withinthe true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, an electric discharge device of cathode pool typehaving a starting electrode, a transformer having a primary inputwinding to be energized with alternating current and a secondary outputwinding, and a saturable core impedance device having a main Winding anda biasing winding, said main winding and said primary winding connectedin series with each other, the circuit of said output winding of saidtransformer being connected across said starting electrode and cathodeof said discharge device, the said biasing winding being adapted to beenergized from a source of direct current, the magnetizing action ofsaid biasing winding being cient to saturate said saturable impedancedevice, the magnetizing action of said main Winding being to and Opposethe magnetizing action of said biasing winding on alternate half cyclesof said alternating current so that said saturable impedance devicetends to pass and suppress current flow on alternate half cycles.

'2. In combination, an electric discharge device of the cathode pooltype having a starting electrode, a transformer having a primary inputWinding energized with alternating current, a secondary output windingconnected to supply a starting potential to said starting electrode, anda biasing winding energized with direct current, the magnetizing actionof said biasing winding being in opposition to the magnetizing elfect ofalternate half cycles of said alternating current, and a saturable coreimpedance device having a main Winding and a biasing winding, said mainwinding and said primary being connected in series with each other, saidbiasing Winding of said saturable core impedance device being energizedfrom a source of direct current of suiiicient magnitude that saidbiasing winding saturates said .saturable impedance device and themagnetizing action of said main winding is to aid and oppose themagnetizing action of said biasing winding on alternate half cycles ofsaid alternating current so that said saturable impedance device tendsto pass and suppress current flow on alternate half cycles, themagnetizing effect of said transformer and saturable impedance biasingwindings being to oppose the magnetizing effect of alternate halfcycles.

3. A circuit for energizing the starting electrode of a cathode pooltype electric discharge device, comprising a transformer having aprimary input winding to be energized with alternating current and asecondary output winding interconnected with the starting electrode, anda saturable impedance device having a main winding and a biasingwinding, said main winding of said saturable impedance device and atleast a part of a winding of said transformer being connected in seriescircuit relationship with each other, said biasing winding of saidsaturable impedance device being energized with direct current, themagnetizing action of said biasing winding being in opposition to themagnetizing effect of alternate half cycles of said alternating current.

4. A circuit for energizing the starting electrode of a cathode pooltype electric discharge device, comprising a transformer having aprimary input winding to be -,ener+ gized with an alternating currentand .a ;secondaryout put winding interconnected with the startingelectrode, and a .saturableimpedance devicehaving a main winding and abiasing winding, said main winding of said saturable impedance ,devicebeing connected in series with said primary input winding, said biasingwinding of said saturable impedance .device being energized ,with directcurrent, the magnetizing action of said biasing winding being .inopposition to the magnetizing .action .of alternate half cycles .of saidalternating current.

.5.. A circuit .for energizing .the starting electrode .of a cathode,pool type electric vdischarge device comprising a transformer having aprimary input winding energized from an alternating current source, asecondary output winding interconnected with .the starting electrode,and a biasing winding energized .from a direct current source, themagnetizing action of :said biasing winding being .in opposition :to.the magnetizing efiect of alternate half cycles of said alternatingcurrent, .and Ya saturable impedance device having a main windingconnected in series with said primary winding and -a biasing windingarranged tobe energized from a direct current source, the magetizingeffect of said biasing winding of said saturable impedance device beingin opposition to the magnetizing efiect of alternate half cycles of saidalternating current, the magnetizing effect of said biasing windings ofsaid saturable impedance device and said transformer beingin oppositionto alternate half cycles of .said alternating current on theirrespective devices.

6. In combination, a pair of electric discharge devices of the cathodepool type having .a starting electrode, said discharge devices beingconnected to conduct on alternating cycles of alternating current, apair of transformers, each of said transformers having a primary winding0on n'e'cte'd to be energized from a source of alternating currentenergy-and a secondary output winding connected to supply the startingelectrode potential, and a pair of saturab'le reactance devices, each ofsaid saturable reactance devices having a main winding connected inseries with one of said transformer primary windings and a biasingwinding, said biasing winding on each of said saturable impedancedevices being connected across a source of direct current, said biasingwindings being arranged in such a manner that their magetizing actionaids and opposes the magnetizing action :of the current in theassociated main winding on alternate halt cycles so that each saturableimpedance device tends to pass and suppress current flow on alternatehalf cycles.

In combination, a pair of electric discharge devices of the cathode pooltype having a starting electrode, said discharge devices being connectedto conduct alternate half cycles "of alternating current, a pair oftransformers, each of said transformers having a primary input windingconnected to be energized from a source of alternating current, asecondary output winding connected to supply the starting electrodepotential, and a biasing winding connected to be energized from a directcurrent source, the magnetizing action of said biasing winding being inopposition to the magnetizing action of alternate half cycles of saidalternating current source and in opposition to the magnetizing eflectof opposite half cycles with respect to each other, and a pair ofsaturable reactance devices,'each of said saturable reactance deviceshaving a main winding and a biasing winding, the main winding of eachsaturable reactance device being connected in series with one of saidtransformer primary windings, said reactance biasing winding beingconnected across a direct current source, said biasing windings beingarranged in such a manner that their magnetizing action aids and opposesthe magnetizing action of the current in the associ ated main winding onalternate half cycles so that each saturable impedance device tends topass and suppress current flow on alternate half cycles and in such amanner that their magnetizing action opposes the magnetizing ac- 7 tionof the current in the associated primary winding on opposite halfcycles.

8. In combination, a voltage peaking circuit for producing analternating voltage which is symmetrical with respect to positive andnegative half'cycles and which is of peak wave form, an electricdischarge device of the cathode pool type having a starting electrode, atransformer having a primary input winding connected to said peakingcircuit for energization thereby and a secondary output windingconnected to supply a potential to said starting electrode and asaturable reactance device having a main winding connected in serieswith said primary winding and in a biasing winding connected to beenergized by a direct current source, the magnetizing action of saidbiasing winding being sufficient to saturate said saturable reactancedevice, the magnetizing efiect of said main winding being to aid andoppose the magnetizing effect of said biasing winding on alternate halfcycles of said alternating current source so that said saturableimpedance device tends to pass and suppress the current flow onalternate half cycles.

9. In combination, a voltage peaking circuit for producing analternating voltage which is symmetrical with respect to positive andnegative halt cycles and which is of peak wave form, an electricdischarge device of the cathode pool type having a starting electrode, atransformer having a primary input Winding connected to said peakingcircuit for energization thereby, a secondary output windinginterconnected with the starting electrode, and a biasing windingenergized with direct current, the magnetizing action of said biasingwinding being in opposition to the magnetizing action of alternate halfcycles of said alternating current, and a saturable reactance devicehaving a main winding connected in series with said primary inputwinding and a biasing winding connected to be energized with directcurrent, the magnetizing action of the biasing winding of said saturablereactance device being sufiicient to saturate said saturable reactancedevice and of a sense to aid and oppose the magnetizing efiect of saidmain winding on alternate half cycles of said alternating current sothat said saturable reactance device tends to pass and suppress currentflow on alternate half cycles, the magnetizing efiect of saidtransformer biasing winding and said saturable reactance biasing windingopposing the magnetizing action of alternate half cycles of saidalternating current in their associated places.

10. In combination, a voltage peaking circuit for producing analternating voltage which is symmetrical with respect to positive andnegative half cycles and which is of a peaked wave form, a pair ofelectric discharge devices of the cathode pool type having a startingelectrode, said discharge devices being connected to conduct alternatehalf cycles of alternating current, a pair of transformers, each of saidtransformers having a primary input winding connected to said peakingcircuit for energization thereby and a secondary output windinginterconnected with said starting electrode, and a pair of saturablereactance devices, each of said saturable react ance devices having amain winding and a biasing winding, the main winding of each of saidsaturable reactance devices being connected in series with one of saidprimary input windings, each of said biasing windings being connected tobe energized by a source of direct current, said biasing windings beingarranged in such a manner that their magnetizing eifect aids and opposesthe magnetizing efiect of the current in the associated main winding onalternate half cycles so that each saturable reactance device tends topass and suppress current flow on alternate half cycles.

11. In combination, a voltage peaking circuit for producing analternating voltage which is symmetrical with respect to positive andnegative half cycles and which is of a peaked wave form, a pair ofelectric discharge devices of the cathode pool type having a startingelectrode, said discharge devices being connected to conduct alternatehalf cycles of alternating current, a pair of transformers, each of saidtransformers having a primary input winding connected to said peakingcircuit for energization' thereby, a secondary output windinginterconnected with the starting electrode, and a biasing windingenergized with direct current, the magnetizing efiect of said biasingwinding being in opposition to the magnetizing efiect of alternate halfcycles of said alternate current, and a pair of saturable reactancedevices, each of said saturable reactance devices having a main winding,a biasing winding, a main winding of each saturable reactance devicebeing connected in series with one of said primary input windings, saidbiasing windings on each of said saturable impedance devices beingconnected across a direct current source, said reactance biasingwindings being arranged so that their magnetizing action aids andopposes a magnetizing action of current in the associated main windingon alternate half cycles so that each saturable impedance device tendsto pass and suppress the current flow on alternate half cycles,

the magnetizing action of each reactance biasing wind-' ing and thetransformer biasing winding of the transformer in series circuitrelationship with the individual saturable reactance device opposing themagnetizing action of current in the associated device on alternate halfcycles.

No references cited.

